Genetics of Philaenus colour polymorphism: the 28 genotypes.

308 BRIEF REPORTS Tabk I. Number of breaks in colcemid treated ment, both relative to the HBSS treatment and cells the untreated controls. The increase was not significant statistically. 100 cells scored for each concentration Acknowledgmmts. - This work has been supported by Cone. Total numwith Breaks Or gaps grants from the Nilsson-Ehle foundation. My sincere X 10-6 ber of breaks breaks or per affected thanks are due to prof. A. Levan for valuable help and mol/l and gaps gaps cell criticism. 10 26 15 1.73 7 15 8 1.88 5 20 II 1.82 2.5 25 I1 2.27 1.4 22 I2 1.83 HBSS 19 15 1.27 Control 6 6 I .oo tude as that of butyl mercury bromide, which was determined to 0.05-0.1 X lo-@ M by FAHMY (1951). The response of Chinese hamster cells to organic mercury compounds would be expected to approximately the same, judging from the results of FISKESJO (1971), who found similar threshold concentrations for other mercury compounds in different test systems. The threshold value of HMB for c-mitosis in Chinese hamster cells was somewhat higher than corresponding values in the Alliirrn test. The strength of the effects decreased with falling concentrations. Fig. 1 shows that there was a correlation between the concentration of HMB and the manifestation of cell damage. Toxic and c-mitotic cells were found mostly in the strongest concentrations. The transitions was gradual between c-mitosis and normal mitosis. The number of chromosome breaks was clearly elevated both in the treatments with HMB and with HBSS. This effect was probably due to the starvation the cells were submitted to during the treatment. In the affected cells, however, the number of breaks and gaps per cell was higher in the HMB treatInstitute of Genetics, University of Lund, Sweden Literature cited BOYER, P. D. 1959. Sulfhydryl and disulfide groups of enzymes. -~~ In The Enz.vmes 2 ecl. (Eds. BOYER, LARDY and MYRBACK), Vol. I, Acad Press, New York, p. 51 1588. FAHMY, F. Y. 1951. Cytogenetic analysis of the action of of some fungicide mercurials -- Ph. D. Thesis, Inst. Genet., Lid, Sweden. FISKESJO, G. 1969. Some results from Allium tests with organic mercury halogenides. - Hereditas 62: 314-322. - 1970. The effect of two organic mercury compounds on human leukocytes in vitro. - Ibid. 64: 142-146. - 1971. The effect of two mercury compounds on lysogenic E. coli K39 (k). - Ibicl. 69: 135138. KRISTOFFERSSON, U. 1971. The effect of cyclamate and saccharin on the chromosomes of a Chinese hamster cell line. lbid. 70: 271 -282. LEVAN, A. 1971. Cytogenetic effects of hexyl mercury bromide in the Allium test. - J. Indian Bot. SOC. 50A: 340 --349. RAMEL, C. 1969. Genetic effects of organic mercury compounds I. Cytological investigation on Alliuni roots. - Hereditas 61: 208 -230. RAMEL, C. and MAGNUSON, J. 1969. Genetic effects of organic mercury compounds 11. Chromosome segregation in Drosophila melanogaster. - Ibid. 61: 231-254. RUNNSTROM, J. and MINELLI, H. 1964. Induction of polyspermy by treatment of sea-urchin eggs with mercurials. - Exp. Cell Res. 35: 157 STEINEGGER, E. and LEVAN, A. 1947. Constitution and c-mitotic activity of iso-colchicine. - Hereditas 33: 385 -396. 193. Ulf Kristoffersson Institute of Genetics S-223 62 Lund, Sweden 0. HALKKA, L. HALKKA, R. HOVINEN, M. RAATIKAINEN and A. VASARAINEN; Genetics of Philaenus colour polymorphism : the 28 genotypes (Received January 13, 1975) In a recent article on the genetic basis of colour relationships was presented (HALKKA et al. 1973). polymorphism in the meadow spittlebug, PhilaeThe results of the crosses performed in 1972 and nus spumaritrs (L.) (Homoptera), a hypothetical 1973 were not then available; they corroborate scheme of the dominance and co-dominance practically all the relationships proposed in the Hereditas 79. 1975 BRIEF REPORTS 309 Table I. Allele combinations and the corresponding phenotypes in Philaenus spurnarius. The subscripts denote: PT PM PL PF PC PO Pt PT PM tri I typ PL tri mar tYP tYP7 tYP tri I tri4 1 tri 6 mar mar mar 5 mar 5 mar lat6 typ I typ I typ Pt tri mar lat f la 2 Ice lop3 K 0) experimental evidence lacking 1) experimental evidence considered insufficient 2) genotype also expressed (or believed to be expressed) aspa and gib in most individuals with appropriate modifier genes 3) genotype also expressed (or believed to be expressed) as qua and alb in most individuals with appropriate modifier genes 4) median stripe often truncated at anterior end 5) thepa dots, or at least the anterior dots are present in most individuals as indentations in the pale elytral margins 6) the flu or qua dots (see also notes 2 and 3), or at least the anterior dots are present as indentations in the pale 7) genotype also expressed (or believed to be expressed) as qua elytral margins in some individuals with appropriate modifier genes Hereditas 79, 1975 3 10 BRIEF REPORTS scheme. In these years, 186 successful crosses were performed. They produced a total progeny of 3799 individuals. With seven alleles, as in Philaenus, there are 28 possible genotypes (7 homozygotes and 21 heterozygotes). In Table 1, all the possible combinations are shown separately for males and females. As explained in detail in the previous article (HALKKA et al. 1973), the same genotype often produces dissimilar phenotypes in the two sexes. In the table, the names of the phenotypes are abbreviated as in our earlier paper (see HALKKA et al. 1973 for the full names). If no superscript is attached to the phenotype designation, the genotype-phenotype correspondence (g-p) has been verified by Mendelian F, ratios and backcrosses. Superscript “0” means that there is no firm experimental evidence for the g-p presented. In these instances, the phenotype suggested is hypothetical, the evidence being circumstantial. Other superscripts imply that the evidence for the g-p presented is based on insufficient evidence (e.g., Mendelian ratios from small progenies), or that complexities of penetrance or expression exist. Some of the complexities are caused by nonallelic modifier genes (see HALKKA et al. 1973). The effect of some of the modifiers on pigmentation is dissimilar in different geographical regions, and forms of expression not mentioned in the table may occur in some natural populations. Such details do not obscure the fact that, with the help of Table 1, it is possible to calculate allele frequencies from practically every sample collected from natural populations in northern Europe, Asia and North America. In Southern and Central Europe, many additional phenotypes are found, but most of them occur at very low frequencies (RAATIKAINEN 1971). In most of the populations investigated throughout the world so far the three homozygotes with unidentified phenotypes (superscript “0”) in Table 1 are very rare. Their frequencies usually are within the range 0.0050.0001. In fact, all the combinations except pt/pt can be considered infrequent in natural populations. In Denmark, Finland, Norway and Sweden the frequency of the allele pt is often as high as 0.9. Very high pt frequencies are similarly found in other parts of Europe, and in Asia and North America. As the sexes areequal in number in newly emerged Philaenus adults, significant inaccuracy is not introduced if only the female sex is used in determinations of allele frequencies for the whole species. This is often necessary, because many of the alleles are expressed only in the females. Ten years ago, HUTCHINSON (1964) wrote on Philaetius that “- - - no clear understanding of the whole situation, which may well prove to be one of the most dramatic examples of polymorphism, will be possible without genetic knowledge - - - -”. Although the “genetic knowledge” called for by HUTCHINSON will not cover the most minute details for many years, the information presented in Table 1 signifies a decisive breakthrough in the understanding of polymorphic equilibria in the spittlebug. The many complexities of genetic determination revealed by the table are less deterrent than they seem. This is so because in most natural populations the “clear” genotypes stand for well over 90y’ of the gene pool. Acknowledgntents - Most of the work was performed at the Department of Pest Investigation, Agricultural Research Centre, Tikkurila, Finland. Without the facilities generously provided by the former and present Heads of this Department, Professors Veikko Kanervo and Martti Markkula, the work would not have been possible. In various phases of the work, we have been aided by Sirno Hovinen and Tarja Kohila The study has been supported by grants from the University of Helsinki and from the National Research Council for Sciences of the Academy of Finland. Department of Genetics, University of Helsinki, (M.R.) Department of Biology, University of Jyvaskyla and (A.V.) Department of Pest Investigation, Agricultural Research Centre, Tikkurila, Finland Literature cited HALKKA, O., HALKKA, L , RAATIKAINEN, M. and HOVINEN, R. 1973. The genetic basis of balanced polymorphism in Philaenus (Homoptera). - Hereditas 74: 69 -80. HUTCHINSON, G. E. 1964. A note on the polymorphism of Philaenus .cpumarius (L.) (Homopt., Cercopidae) in Britain. -~ Entomol. Monthly Mag. 99: 175 -178 RAATIKAINEN, M. 1971. The polymorphism of Philaenus spumarius (L.) in northern Italy. - Ann. Entomol. Fenn. 37: 72-79. Olli Halkka Department of Genetics P. Rautatiekatu 13 SF-00100 Helsinki 10, Finland Hereditas 79, 1975